1. Field of the Invention
The present invention relates to a magnetic random access memory (MRAM) of a spin-transfer magnetization reversal type.
2. Description of the Related Art
A magnetic random access memory is a device which stores binary 1 or 0 utilizing the magnetoresistive effect to cause memory operation. This memory is evaluated as one of universal memory device candidates having a nonvolatile property, high integration, high reliability, low power consumption and high-speed operation.
Recently, regarding a magnetic random access memory, a writing method using a spin-transfer magnetization reversal technique is proposed by Slonczewski (see U.S. Pat. No. 5,695,864). In the spin-transfer magnetization reversal technique, there is a spin-polarized electron having two electron spin directions which contributes to magnetization of a recording layer depending on the direction of current. The spin-polarized electron acts on the magnetization of the recording layer to reverse the magnetization of the recording layer.
In such a spin-transfer magnetization reversal, since the amount of current required for writing is proportional to the volume of a magnetic tunnel junction (MTJ) element, the amount of the current required for writing decreases as the size of the element decreases. On the other hand, as the volume of the MTJ element decreases, the resistance to a magnetization reversal due to thermal agitation decreases. Accordingly, in a 1T1R (one transistor [T] and one magnetoresistive element [R])-type magnetic random access memory of a conventional example, it is considered that advancement in micro-fabrication would increase the possibility of a soft error (erroneous writing or the like) in a non-selected cell by charging and discharging in read and write operation.